The End of Sanctuary: The Evolution of Homeland Defense

On March 23, 1983, President Reagan appealed to the American people to embrace a new vision of national security, one not solely reliant on the threat of nuclear retaliation. Announcing the Strategic Defense Initiative, he reasoned that technological advances could stop “ballistic missiles before they reached our own soil or that of our allies,” even as he acknowledged the effort could “take years, probably decades.”¹ More than forty years later, elements of that vision have been realized. Yet the strategic environment has changed profoundly, and further industrial advances have positioned the United States to achieve what Reagan only imagined.

For decades, U.S. homeland defense rested on two powerful advantages: geography and deterrence. Oceans made direct attacks difficult, while the threat of nuclear retaliation discouraged aggression.

Today, advances in missiles, drones, hypersonic weapons, and other long-range systems are eroding those advantages.² Last fall, China debuted roughly a dozen missile systems, many capable of reaching the United States, while conflicts in Ukraine and the Middle East have shown how drones and missiles can be combined in large-scale attacks against targets previously beyond reach.³ The United States now faces a broader range of threats launched from greater distances, along more complex and unpredictable trajectories, and increasingly in coordinated attacks designed to overwhelm defenses.

Against this backdrop, the Trump Administration’s Golden Dome for America initiative—a proposed “next-generation missile defense shield” to protect the homeland—has sparked debate.⁴ Supporters argue that evolving threats require stronger homeland air and missile defenses, and that technological advancements and two decades of operational practice make such an effort feasible.⁵ Critics question the architecture, costs, and implications for strategic stability.⁶

There is a path forward that makes Golden Dome an executable program. The near-term opportunity is to build on capabilities already in the field and programs underway, integrating them together into a more effective homeland defense network, while laying the groundwork for more expansive and ambitious capabilities that keep pace with the threat while becoming more economical.

Delivering Near-Term Capability

In May 2025, President Trump stated that Golden Dome “should be fully operational” before the end of his term.⁷ A fully operational, nationwide missile shield in three years is hard to envision. A substantially stronger homeland air-and-missile defense network built on existing and already planned capabilities is not.

The building blocks exist. The Pentagon operates missile warning satellites, a global network of radars, and 44 ground-based interceptors in Alaska and California designed to counter long-range missile threats. Battle-proven military systems such as Aegis, THAAD, and Patriot can provide additional defensive layers if deployed domestically, while federal air, maritime, and border surveillance assets, and counter-drone systems, expand coverage of the homeland.

Many of the capabilities associated with Golden Dome were already in development before the initiative was announced, and are now being accelerated with FY25 reconciliation funds.⁸ These include a new satellite constellation to track advanced missiles in flight and create firing solutions, a proliferated space-based sensor network to track moving targets on the ground, upgraded surveillance radars, improved communications systems, and next-generation interceptors.⁹

The near-term challenge is one of integration. Golden Dome’s program manager, General Michael Guetlein, has described it as less a technology issue than a culture and organizational one.¹⁰ Connecting military, intelligence, and civilian systems into an operational network that can track threats and coordinate responses in real time will require extensive testing, new operational concepts, and clear authorities across military organizations and federal agencies, including who is responsible for engaging threats.

Automation, AI, and advanced computing will be essential to the architecture’s operational feasibility. Modern threats move too quickly and at too great a scale for operators to respond without machine-assisted support. Success will also depend on less visible tasks such as accelerating contracting, approving software for government networks, and processing security clearances for industry partners.

If the objective for 2028 is an initial operational “command and control layer” capable of connecting sensors, interceptors, and decision-makers—as General Guetlein has indicated—then the foundation of an expandable Golden Dome architecture is achievable.¹¹

The Feasibility of Space-Based Interceptors

Improving today’s defenses is necessary, but it does not fully address the challenge. One of Golden Dome’s central ideas is early engagement: disrupting threats before launch or intercepting missiles in boost phase, before they release warheads or begin maneuvering. Because that window lasts only minutes, the architecture points toward space, where space-based interceptors (SBIs) could provide global coverage and rapid response.

However, SBIs are the most contentious element of Golden Dome: technically complex, costly, and operationally unproven.¹² A 2004 American Physical Society study deemed them “impractical,” not because the technology was impossible, but because the U.S. industrial base could not produce the “thousand or more interceptors” required or sustain “at least a five- to tenfold increase” in space launches.¹³ Two decades later, that assessment warrants reconsideration. SpaceX has transformed launch cadence and costs, and demonstrated high-volume satellite production, while an expanding space industrial base has created options unavailable a generation ago.

None of this guarantees success. But for the first time since Brilliant Pebbles was canceled in 1993, the United States is seriously testing whether SBIs can be built and fielded at a reasonable cost. FY25 reconciliation funding allocated $5.6 billion to “space-based and boost phase intercept” development.¹⁴ The Space Force awarded prototype contracts and industry is testing relevant technologies, as they progress towards a 2028 demonstration date.¹⁵ Testifying before Congress, General Guetlein emphasized, “if we cannot do it affordab[ly], we will not go into production.”¹⁶

The Problem of Economics and Scale

Even if all the technology works, Golden Dome must still solve the problem of economics and scale. Cost estimates range from $185 billion by the program office to $1.2 trillion over 20 years from the Congressional Budget Office (CBO), with other estimates exceeding $6 trillion.¹⁷ In response, Guetlein remarked, “they’re not estimating what I’m building.”¹⁸ But at the unclassified level, neither the architecture nor the assumptions behind those estimates—capabilities, quantities, timelines, or industrial capacity—have been shared. Even CBO acknowledged it is “impossible to estimate the long-term cost” without greater detail. But the exchange underscores a fundamental point: cost will depend heavily on architectural choices, lowering the cost-per-kill, and operational tradeoffs.

One architectural question is how to adapt existing systems for homeland defense to provide the “underlayer and terminal-phase intercept capabilities” identified in the 2025 Executive Order.¹⁹ Simply multiplying these systems across the country would quickly become unaffordable.²⁰ Systems designed for expeditionary operations and austere environments can be simplified and disaggregated for fixed-site homeland defense, relying on networked sensors and shared infrastructure.

These systems also face a cost-exchange problem: expending million-dollar interceptors against lower-cost threats.²¹ Recent conflicts have exposed how quickly inventories can be depleted under sustained attack. During the 2025 Israel-Iran conflict, roughly a quarter of available THAAD interceptors was reportedly expended in just 12 days.²² Recent U.S. operations in the Middle East have further drained interceptor inventories. Replenishing regional stockpiles will take years and adding homeland defense stockpiles will extend those timelines absent a significant surge in munitions production.²³

That imbalance is why Golden Dome leaders emphasize affordability, magazine depth, and reducing the cost-per-kill.²⁴ These could come through lower-cost munitions, larger production runs, or entirely new technologies. Sustained investment in research and development, especially in directed energy, electronic warfare, and other non-kinetic capabilities should be central to that effort. Improving the economics of defense may prove just as important as improving performance.

The Long Game

Golden Dome should be viewed not as a monolithic system but as an evolving, adaptable architecture. Layered defenses—combining space-based and terrestrial systems—create multiple opportunities to detect, track, and engage threats, while allowing new capabilities to be added over time. But even an evolutionary approach requires discipline in prioritization and sequencing: fielding an integrated command-and-control layer first, expanding sensor coverage and interceptor production next, and only then layering in more ambitious capabilities such as SBIs.

These choices also carry strategic tradeoffs. More capable defenses will not replace nuclear deterrence, nor should they promise perfect protection. But they can limit damage, complicate adversary planning, and reduce confidence that attacks on the homeland will succeed. Such active defenses force opponents to consider higher levels of escalation to achieve their objectives—making an already grave decision even more unpalatable. By reducing confidence in an adversary’s ability to strike the homeland cleanly or cheaply, defenses can reinforce deterrence. They also provide decisionmakers greater time and flexibility in a crisis, reducing pressure for immediate escalation following a missile or drone strike.

Ultimately, Golden Dome will succeed or fail less on technological ambition than on sustained execution and strategic clarity.²⁵ As Reagan understood, it will require persuading the American people, clearly articulating the problem and proposed solution, and building broad political support over time. It will also demand disciplined acquisition, industrial capacity, and hard prioritization amid competing defense demands.²⁶ The most credible path forward is incremental: build on existing capabilities, invest in technologies that improve the cost equation, and deliver concrete gains to homeland defense without crowding out other defense priorities.